1. Field of the Invention
The present invention relates to a wetting agent for semiconductors, which reduces microdefects and a polishing composition employing it. Further, the present invention relates to a method for polishing semiconductor substrates, metal films and a surface having an insulating layer formed thereon with the polishing composition.
2. Discussion of Background
In recent years, along with the progress in the integration and speed of ULSI, etc. to be used for computers, a design rule of semiconductor devices has been progressively refined. Accordingly, the focal depth in device production processes has become shallow, and requirements for reduction of defects on semiconductor substrates and for smoothness of semiconductor substrates have become strict.
In recent years, as defects to impair device properties, scratches having a depth of a few nm, or dotted- or line-form projections having a height of a few nm, have been concerned. Surface defect inspection devices for detecting such microdefects have been therefore developed. Defects on a wafer surface which was polished with a conventional polishing composition were inspected by an inspection device having ability to detect such microdefects, and as a result, it was found that nano order defects which could not be detected by conventional methods were present on the polished substrate surface.
Even though polishing compounds based on relatively new techniques were used, such surface defects were similarly formed. For example, as a technique to reduce surface defects, Patent Documents 1, 2 and 3 disclose a polishing composition comprising colloidal silica, an alkaline compound and a water soluble polymer compound, for polishing semiconductor substrates. However, according to the study by the present inventors, in a case where polishing is carried out with the polishing composition disclosed in the above Patent Documents, the above-mentioned nano order defects may sometimes be formed, and the cause of such defects is not clearly understood.
Patent Document 1: JP-A-2005-518668
Patent Document 2: JP-A-2006-509364
Patent Document 3: JP-A-2006-352042